The present invention relates to a hydraulic tank reservoir pressure and vacuum stabilizer system, and more particularly to such an hydraulic system utilizing a displacement-type hydraulic element adapted to receive fluid from and return fluid to the reservoir.
Hydraulic tanks commonly have an air space provided therein to compensate for the changes in the volume of hydraulic fluid that occurs during operation. For example, when the hydraulic tanks are used with hydraulic jacks, the volume of fluid in the tank fluctuates as the jacks are retracted or extended.
In order to prevent pressure buildup or the creation of a vacuum within the tank, many of the earlier hydraulic systems had the air space communicating with the atmosphere through a vent or the like. However, one of the drawbacks of such vented systems was that the air moving in and out of the tank during operation carried in dust particles and water vapor, which materials became entrapped within the fluid. Even though a breather filter was used in certain systems, dust and water vapor still accumulated within the fluid. Accordingly, such systems have not been entirely satisfactory.
In order to prevent the contamination of the fluid by airborne particles, some of the recent hydraulic systems utilized a sealed hydraulic tank reservoir. However, tank size must be greatly increased to obtain adequate air volume so that the pressure differentials within the tank which occur during operation are minimized. The increased size of the tank takes up valuable space in the vehicle and frequently reduces operator visability. Thus, it is seen that an improved hydraulic tank is needed for use in a system having a displacement-type hydraulic element in communication with the tank, which will enable fluid to move into and out of the tank without substantially changing the air pressure therein, yet which has provision for positively preventing particle and water contamination of the hydraulic fluid.